That sum has been pushed up to $21.8 billion, but as Recode points out, that's due to Facebook's stock rising over the last few months.

With the deal now official WhatsApp founder Jan Koum has joined the Facebook board, though the specifics of his role are currently unknown.

We're all curious to see if and how Facebook will play around with WhatsApp, but we expect it won't meddle much for the time being. Zuckerberg promised that, as with Oculus, WhatsApp will continue to operate largely independently.